Keto thiophanes and method of preparing same



Patented July 12, 1949 KETO THIOPHANES AND METHOD OF PREPARING SAME Bernard R. Baker, Nanuet, N. Y., assignor,-by mesne assignments, to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application June 21, 1945, Serial No. 600,830

3 Claims. 1

The present invention relates to thiophanes and to methods of preparing the same.

I have found that I can prepare certain types of thiophanes by condensing a monoor dicarboxylic thio ester with an unsaturated monoor dicarboxylic acid ester in accordance with the following general equation:

S'Hi

wherein R is alkyl, R is carbalkoxy and R," and R' are hydrogen, alkyl, phenoxyalkyl, carboxyalkyl and carbalkoxyalkyl. When in the above equation either R" or R' or both are phenoxyalkyl I intend to include substituted phenoxyalkyls, such as chlorophenoxyalkyls, bromophenoxyalkyls, nitrophenoxyalkyls, etc.

In carrying out my invention a large number of monoand dicarboxylic thio esters can be used as intermediates, the principal requirement being that the thio group is attached to a carbon atom adjacent to a carbonyl group. Among these may be specifically mentioned: ethyl thioglycolate, methyl thioglycolate, ethyl alpha-thiopropionate, methyl alpha-thiopropionate, ethyl alpha-thiobutyrate, methyl alpha-thiovalerate, ethyl alphathiocaproate, methyl alpha-thiocaprylate, ethyl alpha-thiosuccinate, methyl alpha-thioglutarate, ethyl alpha-thioadipate, methyl alpha-thiopimelate, ethyl methyl 2 mercapto 5 -chlorophenoxyvalerate, and the like.

Similarly, a nurnber of unsaturated esters may 2-mercapto-5-phenoxyvalerate,

be used as the second intermediate in preparing by means of the present invention are new compounds. These may be illustrated by the following general formula:

wherein R and R' are as defined above.

In preparing thiophanes by the process of the present invention I prefer to dissolve the thio ester and the unsaturated ester in an inert solvent such as benzene, ether, dioxane, etc. A strongly alkaline substance such as an alkali metal, alkali metal alcoholate, alkali metal amide, etc. is added to the reaction mixture and serves as a catalyst for the reaction. The mixture is kept under anhydrous conditions.

When in preparing the new compounds of the present invention wherein R is hydrogen and R is alkyl, phenoxyalkyl, etc. I prefer to carry out the reaction at temperatures of from about to about C. When R" is alkyl, phenoxyalkyl, etc. and R is hydrogen I prefer to carry out the reaction at temperatures of about 10 to about 40 0., although, temperatures as high as 120 C. may be used in the reaction. The reaction may require from about 1 hour to about 30 hours to complete, but more usually from 2 to about 5 hours.

When the reaction is complete the products can be recovered from the reaction mixture by acidifying, washing with water, and fractionally distilling the product. I prefer, however, to recover the product by extracting the reaction mixture with ice water and iced aqueous solution of an alkali such as, potassium hydroxide. The aqueous extracts are then acidified and the oil which separates is extracted with a .water immiscible solvent such as benzene. This extract is then fractionally distilled to give a pure product.

These compounds are useful as intermediates in the preparation of antivitamins and vitamins such as biotin.

It will be understood that various modifications may be made in the specific procedures described without departing from the scope of the invention.

Example 1 Tothe dry sodium ethylate from 5.8 g. of sodium obtained by evaporating the alcoholic solution to dryness in vacuo was added in a nitrogen atmosphere 27.5 g. of ethyl thioglycolate in 50 cc. of benzene followed by 33.6 g. of ethyl Z-hexenoate in 25 cc. of benzene. After being refluxed for three hours, the solution was extracted with ice water and iced 3% sodium hydroxide. The aqueous extracts were acidified and extracted with benzene. Distillation gave 33.5 g. (68%) of Z-propyl- 3-carbethoxy-4-ketothiophane, as an oil, boiling point 109-111 C. (1 mm.).

Example 2 To the dry sodium methylate from 2 g. of sodium obtained by evaporating its methanolic solution to dryness in vacuo was added 7 g. of methyl thioglycolate and 13.6 g. of methyl 6-phenoxy-2- hexenoate in 50 cc. of benzene. After being refluxed for two and one-half hours, the solution was extracted with iced waterv and iced 3% sodium hydroxide. Acidification gave an oil which was extracted with benzene, washed with water and evaporated to dryness in vacuo. The.-

product, 2-(gamma-phenoxypropyl). 3 carbQ- methoxyl-ketothiophane, was obtained "as. an orange oil, yield 14.7 g. (81%).

Example 3' A mixture of 33.5 g. of zepropylea-carbethoxyr 4-ketothiophane, 150 cc. of water, 21 cc. of concentrated sulfuric acid and 40 cc. of. acetic acid was refluxed six hours. The cooled mixturewas extracted with benzene, washed with dilute alkali and water, then distilled. The product; fl -propyb 4-ketothiophane, was obtained as a colorless oil, boiling point 98 C,., (12: mm). yield of 1-!-7-.8-.g. (80%) was obtainedl Ewampleit A mixture of 2, g. of 2- (gammarphenoxypropyl) 3-carbomethoxy-.4-ketothiophane, 4-,cc. of acetic acid, 1.6 cc. of water and-2- cc. of concentrated-sulfuric acid was refluxed five hours. The cooled mixture was extracted-with-ether, washed: with dilute alkali; and' water. After. removal, of; the solvent the residue was. crystallized from petroleum ether. Tworecrystallizations f.- the-prodnot, 2 (gamma-phenoxypropyl) e ketothiophane, from petroleum-ether gave white crystals. melting-point; 599-61 C.

Example 5 Example :6

To 25.3 g. of methyl 2-mercapto-5ephenoxyvalerateand 02cc, of niperidine was added, 13 cc. of. methyl acrylateinportions withice cooling so that the temperature. was 40-50 C. After five hours at room temperature, the mixture was dissolved in 150 ccjof dryiether and added to the dry sodium methylate from. 2., g.. of. sodium obtained by evaporating;itsmethanolic solutionto dryness in vacuo. The nearly, clear solutionwas allowed' to standatroom temperature; protected from'moisturefor sixteenahours. The ether. solutionwas extractedthree-times wlthicewater and thecextracts immediately. run. into iced hydrochloric-acid; A; benzene-extract of the oil which had separated was washedtwice withdilutesodium bicarbonate. waten; andthenevaporatedto dryness in vacuo. The product; ZAgamma-phenoxypropyl) -3-ket0-4, carbomethoxythiophane, was obtained as an orange-yellow oil which gave a purple color with alcoholic ferric chloride. The yield was 22:7Fg. (73%);

Example 7 From 155 g. ofmethyl 2,-mercaptoa5-chlorophenoxyvalerate, 8; cc. of methyl :acrylate and the dry sodium methylate from 1.2 g. of sodium was 4 obtained 14.7 g. of Z-gamma-chlorophenoxypropyl) -3-keto-4-ca rbo methoxythiophane in the same manner as described in Example 6 for 2(gamma-phenoxypropyl) -3-keto-4-carbomethoxythiophane.

Example 8 A mixture of 8.3 g. of 2(gamma-carbomethoxypropyl) -3-ke to.-4=-carbomethoxy thiophane (prepared as in Example 5) and cc. of 10% sulfuric acid was refluxed for ten hours, saturated with sodium chloride and extracted twice with ethyl acetate. Evaporation gave, Z-(gamma-carboxypropyl)-3-ketothiophane, as an oil, which was crystallized from benzene. A yield of 2.6 g. melting at 72-73 C. was obtained.

Example 9 To dry sodium ethylate from 26. g. of sodium and500 cc. of absolute ethanolobtainedby evapcrating the solution to, dryness in vacuo'. was added350 cc. of benzene and. 112 cc. (1201s.) of ethyl thioglycolate. The mixture was then heated to boiling and 180 g. of. ethyl maleate wasadded at such a rate that the mixture refluxed spontaneously (five minutes). After being refluxed two hours, thesolution was poured on ice and ethen, The aqueous layer was immediately run into dilute acetic acid and the organic layer extracted four times with ice water (a total of 3 liters). The combined acidified aqueous mixture was extracted with benzene, washed: withwater, aqueous sodium bicarbonate and Water. Distillation'igave a colorless oil boilingl point E139. C. (1. mm), which turned yellow on standing. A Y eld: of 12.? g. (52%-)- of 2,3-dicarbethoxy-4-kel3othicphanewas obtained. The compound gaveva wine-red color with.alcoholicferric chloride.

Example 10 A mixture of 24- g. of 2,3-dicarbeth0xy-4-ketothiophaneand,15,0-cc. of 1.0% sulfuric acid. was refluxed. five hours. The clear yellow solution was: saturated with ammonium. sulfate and ex.- tracted twice with. ethyl acetate. Evaporation gave alquantitative yield of crude product. Becrystallization fromtoluene-gave 12, g. (84 of white crystalsof 4,-ketothiophane-2ecargboxylic acid melting at 132-13 4-" C.

Example 11 To the dry sodiumethylate from 0.95 g. of sodium was added 2.7 cc. of ethyl thioglyc'olatje in 8 cc. of. benzene and 6.2 g. of. ethyl'7-carbethoxy-2- heptenoate in 7 cc. of. benzene. The cooleds'olution, after beingrefluxed for four hours, was ex.- tracted with ice water and the extracts acidified. The .oil was extracted. with benzene, washed, with aqueous sodium bicarbonate andv water. Evaporationgave a yieldof 3.8 g. (46%) of 2-(delta-carbethox ybutyl)-3-carbethoxy-4-ketothiophane as an. oil. The product was characterized .as. its crystalline semicarb'azone; melting point 130"- 1.3390.

Example 12,

Tea suspension of 20 g. of" sodium-methox ide in cc. of benzene Was added22 cc. ofmethyl thioglycolate followed by 27.7 g. of methyl glutaconate in 50 cc. of benzene. The mixture was refluxed for two hours during which time an oil separated. The mixture was cooled in ice and extracted twice with iced water, the extracts being immediately run into dilute hydrochloric acid, The. oil was extracted, with benzene, washed with aqueous sodium bicarbonate and wherein R is an alkyl radical and R' is a carbalkoxyalkyl radical which comprises heating an alkyl ester of thioglycollic acid with a compound having the formula:

c-oooR RIII I H wherein R and R are as defined above, in the presence of a compound selected from the group consisting of alkali metals, alkali metal alcoholates and alkali metal amides and an inert organic solvent.

3. A method of preparing Z-carbomethoxymethyl-3-carbomethoxy-4-keto thiophane which comprises heating methyl thioglycolate with methyl glutaconate in the presence of sodium methoxide and a suitable solvent.

BERNARD R. BAKER.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,416,100 Karrer Feb. v18, 1947 2,417,826 Schnider Mar. 11, 1947 2,418,923 Bernstein Apr. 15, 1947 2,424,007 Moore July 15, 1947 2,438,807 Karrer Mar. 30, 1943 FOREIGN PATENTS Number Country Date 567,438 Great Britain Feb. 19, 1945 66,563 Norway Aug. 2, 1943 

